This invention relates to cutting tools, and more particularly to a retention system for retaining such tools in a support block during use.
Cutting tool assemblies for such applications as continuous mining or road milling typically comprise a cutting tool, sometimes called a cutting bit, rotatably mounted within a support block. The support block in turn is mounted onto a drum or other body, typically by welding, which in turn is driven by a suitable drive mechanism. When a number of such support blocks carrying cutting tools are mounted onto a drum, and the drum is driven, the cutting tools will engage and break up the material which is sought to be mined or removed. The general operation of such a mining machine is well known in the art.
Because the support block is exposed, it is subject to wear and abuse and must be cut or torched off the drum and replaced when unusable. In order to prolong the life of the support block, a cutting tool holder, sometimes referred to as a bit holder, tool sleeve, or bit sleeve, is sometimes employed. The cutting tool is mounted within the tool holder which in turn is fixedly held within the support block via some mechanical connection. The tool holder generally has an outer wear surface which helps to protect the support block from abuse and wear, thus minimizing or eliminating the down time periods otherwise required for drum repair. The use of such tool holders is well known in the art. For example, U.S. Pat. No. 5,067,775 to D'Angelo discloses the use of such a bit holder which is referred to as a sleeve in that patent.
Various methods have been proposed or used in the past to rotatably mount a cutting tool within a support block, or alternatively, within a tool holder which in turn is fixedly held within a support block.
For example, U.S. Pat. No. 3,519,309 to Engle et al. discloses a cutting tool retained by a captive keeper ring within a support block. More specifically, and as illustrated in FIGS. 10, 11 and 12 of the Engle et al., the cutting tool has a cylindrical shank which defines an annular shank groove adapted for receiving resilient keeper member. The keeper member as shown comprises a split keeper ring made of, for example, spring steel and has a plurality of projections distributed around its perimeter. The support block has a main bore for receiving the shank of the cutting tool. The main bore of the support block is provided with an annular block groove for receiving the projections of the keeper ring when the shank of the cutting tool is forcibly pushed into the main bore of the support block. Such a retention method is generally known and used in the art.
The cutting tool retention method disclosed in the Engle et al. patent requires that force must be applied to the cutting tool, as the cutting tool shank is inserted into the main bore of the block, in order for the resilient keeper member to be compressed within the main bore of the support block until it expands into and engages the annular block groove. A similar force in the opposite direction must be used to remove the cutting tool from the main bore of the block and if such a force is applied to the tool during operation the cutting tool would be accidentally dislodged. Because the annular shank groove is not sealed or otherwise protected to keep dirt or dust from interfering with the proper operation of the resilient keeper member, such dirt or dust could interfere with the insertion, or especially the removal, of the cutting tool. Lastly, this retention method requires that the cutting tool, the most often replaced component of a cutting tool assembly, include a separate resilient keeper member component which complicates the manufacture of such cutting tools and increases the cost.